Roll baling machines such as disclosed in U.S. Pat. No. 3,815,345 have used guide members to support a bale forming apron in order to define an initial shape for an expandable bale chamber. These guide members are movable between an extended position inside the bale chamber where they support the apron and a retracted position outside the bale chamber. The guide members are constantly urged toward their extended positions by springs. This constant urging of the guide members results in bale damage such as scuffing and hollowing out of bale ends during formation. Furthermore, this constant urging of the guide members interferes with the discharging of bales from the machine.
The present invention overcomes these problems by providing that the guide members are movable from their extended positions to their retracted positions during bale formation without being opposed by the springs which remain relaxed and by providing that the springs exert force to urge the guide members toward their extended positions only after a bale that is formed in the bale chamber has cleared the guide members during the discharge of the bale from the machine. In other words, the springs do not constantly urge the guide members toward their extended positions, but they do apply force to return the guide members to their extended positions at a predetermined point during bale discharging. The guide members are maintained in their extended positions by the bale forming apron which rests thereon to define the initial shape for the expandable bale chamber.